Poloxamer 188

     [9003-11-06]; This product is an α-hydro-ω-hydroxypoly(oxyethylene)a-poly(oxypropylene)b-poly(oxyethylene)a block copolymer.

     It is prepared by the reaction of propylene oxide with propylene glycol to form polyoxypropylene glycol, followed by the addition of ethylene oxide to form a block copolymer. In the copolymer, the number of oxyethylene units (a) is 75–85, the number of oxypropylene units (b) is 25–30, the oxyethylene (EO) content is 79.9%–83.7%, and the average molecular weight is 7680–9510. 

     【Description】  This product is a white or almost white, translucent waxy solid; with a slight characteristic odor.     It is freely soluble in water and in ethanol, soluble in anhydrous ethanol or ethyl acetate, and practically insoluble in petroleum ether.    

     【Identification】  The infrared absorption spectrum of the substance corresponds to that of the reference spectrum (Spectrum 618).

    【Tests】Acidity or alkalinity  Dissolve 1.0 g in 10 ml of water, and determine as directed (General Rule 0631); the pH should be 5.0–7.5. Clarity and color of solution  Using the solution from the test for acidity or alkalinity, examine as directed (General Rule 0901 and General Rule 0902); the solution should be clear and colorless. Water ;Determine as directed under the determination of water (General Rule 0832, Method I); not more than 1.0%. Residue on ignition  Ignite 1.0 g as directed (General Rule 0841); the residue is not more than 0.4%. Heavy metals Dissolve 1.0 g in 23 ml of water, add 2 ml of acetate buffer (pH 3.5), and determine as directed (General Rule 0821, Method II); not more than 20 parts per million. Arsenic  Dissolve 1.0 g with 5 ml and 23 ml of water by shaking, and determine as directed (General Rule 0822, Method I); it complies with the requirement (0.0002%).     Bacterial endotoxins (for injection); Determine as directed (General Rule 1143); contains not more than 0.012 EU per mg.     Sterility (for sterile preparations without a sterilization process) Examine as directed (General Rule 1101); it complies with the test. 【Category】  Pharmaceutical excipient, solubilizer, and emulsifier, etc.

       【Storage】;Protect from light, keep tightly closed. ;Appendix: Preparation of solution Dissolve 50 g of vinegar in 900 ml of methanol containing 0.5 ml of glacial acetic acid, dilute to 1000 ml with methanol, and mix well. If it appears yellow, it should not be used; if it appears cloudy, filter it. If it remains cloudy or yellow after filtration, it should not be used. This solution should be prepared immediately before use. Store in a brown bottle, protected from light. Preparation and standardization of phthalic anhydride-pyridine solution Add 72 g of phthalic anhydride to 500 ml of pyridine (the water content of pyridine should be less than 0.1%; or take 500 ml of pyridine, add 30 g of phthalic anhydride, dissolve, and distill, using the middle fraction), shake vigorously until completely dissolved or heat in a water bath at 40°C to complete dissolution, protect from light, and allow to stand overnight. Precisely measure 10 ml of the above solution, add 25 ml of pyridine and 50 ml of water, mix well, allow to stand for 15 minutes, add 0.5 ml of phenolphthalein-pyridine solution (1→100), and titrate with sodium hydroxide titration solution (0.5 mol/L); the consumption of titration solution should be 37.6–40.0 ml.